In the field of printing terminal apparatus, it has been common design practice to use a thermal-type printer along with a keyboard-operated input and a central processing unit for controlling the several functions. While thermal-type printers may include a stationary member containing a plurality of thermal elements, such printers may be of the type which have one or more print heads driven inside-to-side manner and which include thermal elements for printing either in dot matrix or in character form.
Prior thermal-type printers have used the central processing unit as a central controller for the several functions with required storage capacity within the system for enabling the operations in timed manner.
It is desired to increase the print quality and print speed of the thermal-type dot matrix printer and accordingly to provide additional function and features in the system of these printers.
Representative prior art in the field of thermal printers includes U.S. Pat. No. 3,476,877, issued to P. E. Perkins et al. on Nov. 4, 1969, which discloses a teleprinter using thermal printing techniques under the control of a data processor which supplies both clock and information signals to the remote thermal printer. A shift register sequentially stores groups of data bits transmitted from the data processor and binary counting means is used to control the sequential energization of selected groups of the thermal printing elements.
U.S. Pat. No. 4,020,465 issued to M. J. Cochran et al. discloses a thermal line printer having a printer chip which is operated to generate its own internal commands and clock signals, and is interconnected with an arithmetic chip and with a scanning and read-only-memory (SCOM) chip. Auxiliary chips include register chips, a programmer chip and a read-only-memory (ROM) chip. The sequential access memory stores multi-bit words for each character to be printed with a commutator reading the words from memory for each line to be printed. The read only memory (ROM) has a dot matrix code therein for each character, and a time sequencer and decoder connected thereto is synchronized with the commutator to produce a different output from the ROM for each reading of each given word from memory.
It is therefore proposed to control the thermal printer in a manner wherein independent controls are provided for the several functions rather than relying on a central processing unit.